Seed traits and germination in the Cactaceae family: A review across Americas

Abstract

Background: Cactaceae is the fifth taxonomic group with the highest proportion of threatened species and among the angiosperms, the most vulnerable to human disturbance. One way to contribute to the preservation of this family is to understand the processes that promote seed germination. Questions: Have the relationship between seed traits and cactus germination been documented? How common is dormancy and seed banks in Cactaceae? Are there general patterns in cacti germination response to temperature, light, water, salinity, phytohormones, hydration/dehydration cycles, mechanical or chemical scarification? Data description: A total of 333 studies on cactus germination with information on 409 taxa. Study site and dates: since 1939 to January 2020. Methods: A search of scientific articles in Google Scholar was performed with the words Cactaceae, cacti and cactus, in combination with various matters on germination in English, Spanish and Portuguese. Results: The main germination studies in cactus deal with photoblasticism (275 taxa), temperature (205 taxa) and seed longevity (142 taxa). Other lines of study in cactus germination (e.g., desiccation tolerance, vivipary, phytohormones, mechanical or chemical scarification, in vitro germination, hydration/dehydration cycles, water and saline stress, serotiny, storage in cold, high temperature tolerance and soil seed bank) include between 14 and 65 taxa. Cacti have only physiological dormancy and optimal germination for most species occur between 20 and 30 °C. Photoblasticism is strongly influenced by phylogeny with 80.9 % positive photoblastic species. Conclusions: Mexico, Brazil and Argentina are the three leading countries in the study of cactus germination.